Socioeconomic disparities in health are well documented in the United States in that the higher socioeconomic status (SES) a person is the lower level of incidence and the prevalence of health problem, disease and death will be. Researchers have argued that SES disparities in health are found in different races, across countries, and throughout life. Furthermore, some researchers have argued that high SES persons enjoy their active life expectancy until quite late in life, while low SES persons start to suffer morbidity and functional limitation through middle and early old age. As a result, socioeconomic disparity in health becomes increasingly differential at middle age, while it diminishes until later old age due to physical fragility of human being and declining effect of SES. This study extends previous research by applying the Multi Level Model for Change (MLMFC) and Multi Cohorts Accelerate Longitudinal Design (MCALD) to explore SES disparities in health over the life course. Functional limitation and chronic diseases are used as measurements of health status over time. This study introduces a new way to measure health status over time by combining number and duration of chronic diseases. The results suggest that using a combination of number and duration of chronic diseases as measurement of health over time is more optimal than only using the number of chronic diseases. Both time variant and invariant independent variables are used to explore health trajectory. Findings from this study indicate that people from different SES groups have different health trajectories over the life course. Low SES people tend to age faster than their high SES counterparts. The process of aging in the United States is largely segregated according to individuals’ SES. Financial stress and health risk behaviors are two major mediators of SES disparities in functional limitation. However, SES (measured by income) is consistently a significant predictor of chronic diseases after controlling financial stress and health risk behaviors. Findings of this study suggest that the mechanisms through which SES impacts functional limitation may be different from its impact on chronic diseases.